This invention pertains to methods of making ohmic contacts to semiconductors and more particular is concerned with a method of making ohmic contact to ferroelectric semiconductors.
One known method to make ohmic contact electrodes uses a metal or metal alloy which has a work function which matches that of the semiconductor which need to be electroded. Because the work functions of both materials match, no electrical barrier height is formed at the electrode junction and an ohmic contact electrode is thus obtained. It is, however, difficult to find an electrode material which has matching work function to that of a particular semiconducting material and still has satisfactory engineering properties.
Another method calls for having the surface of the semiconducting material heavily doped (either n type or p type), such that the electrical barrier at the electrode junction created due to the mismatch of work function of both materials has a narrow profile and charge carriers such as electrons and holes have no difficulty quantum-tunnelling through the potential barrier. The difficulty is that not all semiconducting materials can be heavily doped without having the dopant charge compensation mechanism changed. If the dopant charge compensation mechanism is changed and the dopants can be charge compensated by defects other than free electrons or holes, a narrow profile of electrical barrier will not be built and no ohmic contact can be formed.
An object of the invention is to provide a method of forming ohmic contact electrodes to semiconductors which does not require work-function matching nor heavy doping.